Communication in a fire detection system is rare unless a pre-fire or fire scenario is occurring. For example, when devices in a fire detection system are sensing alarming levels of heat or smoke, all input devices in the system can transmit alarms and/or data to a gateway. Often, these transmissions can be substantially simultaneous. Accordingly, a cascading wave communication protocol can support communication in these types of worst-case scenarios.
A cascading wave communication protocol works on the principal of data aggregation. For example, a wireless fire detection system can include four sensors S1, S2, S3, and S4. As seen in FIG. 1, a packet transmitted by sensor S4 includes only S4's data. When the packet is received by sensor S3, sensor S3 appends its data to S4's data and transmits the packet to sensor S2. When the packet reaches a panel P, the packet can include data from all four sensors S1, S2, S3, and S4.
A large wireless fire system loop can include any number of devices, for example, N devices. In these systems, the cascading wave communication protocol can support a packet size large enough to aggregate data from all N devices. For example, each communication time slot can be long enough to accommodate a maximum size packet.
To enable efficient data aggregation without increasing message latency, child nodes can be allocated communication time slots before the parent nodes. In FIG. 1, sensor S3 can be a router or parent of sensor S4, sensor S2 can be a parent of sensor S3, and so on. The communication time slots allocated to sensors S4, S3, S2, and S1 can be slot 1, slot 2, slot 3, and slot 4, respectively. Accordingly, a child node's data can always be available at the parent node during the parent node's communication time slot. In this manner, the parent node can aggregate its own data with the data received from its child node. Then, the parent node can transmit the aggregated data together in a single packet.
In some systems, a parent node can have multiple child nodes. However, the communication time slots of all child nodes can occur before the communication time slot of the parent node. Accordingly, a packet transmitted by a parent can contain its own data aggregated with the data or alarms received from all of its child nodes.
Due to the aggregation described above, the transmission of data from four nodes requires four communication time slots. Similarly, the transmission of data from N nodes requires N transmission time slots. In this manner, a control panel can receive data from each of the nodes in the network.
Using the same protocol described above, a control panel can also transmit data to nodes in a network. For example, a fire panel can transmit data to N nodes in a network, and the data can reach each of the N nodes in respective ones of N time slots. When the control panel transmits data to nodes, the slot allocation of the nodes can be reversed.
When a device in a wireless system detects an alarm, the device can transmit data to a gateway. The gateway can be polled by a control panel in a wired system, which, depending on the content of the received data, can activate various output devices. When one of the output devices to be activated is part of the wireless system, the control panel can transmit instructions to the gateway, which can retransmit the instructions to the output device. In these circumstances, the latency time to activate the output device in the wireless system can be the sum of the time for the gateway to receive data from a device, the time for the gateway to transmit data to the control panel, the time for the gateway to receive instructions from the control panel, and the time for the gateway to transmit the instructions to an output device. That is:Ttot=Tinput_gw+Tgw_panel+Tpanel_gw+Tgw_output  (1)
In various situations, the length of this latency time can be problematic. Accordingly, there is a continuing, ongoing need for systems and methods of fast wireless output device activation in a mesh network system.